Loading-coil for telephone-lines.



w. MERZ. LOADING COIL FOR TELEPHONE LINES.

APPLICATION FILED SEPT-i5, 1914.

I Patented May 23,1916.

2 SHEETS-SHEET 1.

//7 V2)? for: W/'///'am Merz LOADING COIL FOR- TELEPHONE LINES.

APPucATmN man 2115,1914.

1,184,001, Patented May 23,191 2 SHEETSSHEET 2.

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WTLLIAM MERE, OF ."BERWYN, ILLINOI$, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OE YORK.

LOADING-COIL FOR TELEPHONE-LINES.

Specification ofLetters Patent.

Patented. May 23, 19H;

Application filed September 15,1914. Serial N 0. 861,901.

telephone systems, it is desirable to combine four line conductors in such a man-.

ner that two two-wire-physical or side cir-= cuits form a third or phantom circuit,

' In. order to load these circuits according to the Pupin system, each side circuit is equipped with a series of loading coils so Wound that they offer to currents in the. phantom'circuit, as nearly as practicable a non-inductive resistance, and the phantom circuit is equipped with loading coils so Wound as to offer to currents in either side circuit, likewise as nearly as practicable, a

non-inductive resistance.

It is usual to inclose loading coils in a cast iron case, this material being desirable because cheap, substantial and weatherresistance to induced electric forces, and

formed into continuous IIOII rings, or they may be continuous non-magnetic rings. In the core of any such loadin'g coil the eddy current and hysteresis losses, dueto small stray fields, are negligible.

Accordin to a known construction and scheme of winding of loading coils for phan-- tom line systems, as described in the Campbell and Shaw Patent No. 980,921, an annu lar core is provided with inner and outer windings of equal number of turns in a plurality of core sections, preferably two and four sections in the side circuit coil and inthe phantom coil, respectively, each line conductor in a coil including serially the inner and the outer windings, respectively of'opposite c'ore sections. With either 0 suclr'coils, butmore especially'in the phan tom coil, there is some magnetic field exterefi'ective, for example,

4 in the windings of a given core section.

This is due to the fact that the outer winding exerts a. stronger external magnetizing force than the inner winding. The resultant external magnetic field, due to opposing currents in the two windings, acts in part. upon the iron case surrounding the coil, and

spends itself to a certain extent in eddy current and hysteresis losses therein, which reacts on the coil and impairs its efllciency.

The external field also acts in part on the conductors of the coil itself, unless these conductors are finely stranded, and causes eddy current losses therein. i i

It is one of the purposes of the invention to minimize these losses.

in loading coils having continuous iron cores, 2'. 6. cores without air-gaps, and is accomplished'by giving each inner winding a sufficient number of turns With respect to the outer'winding on the same section therewith, so that themagnetizing force of the inner winding is increased and the magnetic field, due'to the opposing currents. in the two'windings, is reduced substantially to a minimum in the regions external to the coil. In other Words, this stray magnetic field is virtually driven to the core of the coil, where it can dissipate very little energy instead ofbeing allowed to spend itself in the non-laminated iron of the case and in the outer coil conductors. A

The invention will be more fully understood by reference drawings whereinof the core and windings of three loading coils for a phantom telephone line system, including two side circuit coils and one phantom coil; Fig. 2 is a simplified diagram of a typical four-conductor phantom tele- Figure 1 1s a diagrammatic representation phone line system, loaded with side and phantom circuit coils; and Figs. 3 and 4 are diagrammatic drawings each showing part of a phantom loading coil in crosssection along the: center line of the core, and indicating the distribution of magnetic lines, due to opposing currents in-the wi11d ings of one the stray coil, and structed in accordance with the invention.

Referring first to Fig. 2, the four conductors 1, 2, 3, 4 of a long distance telephone line system are shown connected in a wellquarter section; Fig. 3 indicating field with an ordinary phantom .This purpose is to the accompanying Fig; 4- the stray field in a coil contor 1, includes at each group of coils, in

series, two sectional windings, 24, 25 on a sidecircuit coil and two sectional windings V 26', 27 on a phantom coil. The two sectional windings 26, 27 comprising one line winding element of the phantom coil are, as .indicated inFig. 1, an outer and an inner winding, respectively, of opposite core sections A and 0, each covering approximately a quarter core section. -F or phantom circuit working, the direction of the currents in windings 26 and 27, included in line conductor. 1, and likewise in windings 28 and 29, 36 and 37, and 38 and [39,included in I line conductors 2, 3 and a, respectively, is

such that the magnetizing forces are cumulative, 6., all tending to produce a magnetic flux in the same circular direction in the core 31, and the coil offers the required inductance according to the Pupin system of loading. On the other hand, for'side circuit working, the currents in these windings tend to produce opposite magnetic forces so that the inductance is very small. However, in this casethere will be a resultant stray field occupying the smallspace' (Figs. 3 and 4) between these windings,

spreading at or near their ends 33, 3 1 and returning partly by way of the core 31 and partly by way of the space including the iron case 4:0 external to the coil. It is this external field of force due to opposing currents in the inner and outer windings that causes the eddy current loss in the case and outer winding conductors. I As shown in Fig. 3,-when the 'outerand inner windings have an equal number of turns, the magnetizing force of the. outer winding predomimates inthe space external to the coil, and

the greater number of stray magnetic lines, indicated by the curved lines, interlinlcwith' the caseOg Theseexterna'l stray magnetic forces. can, however, be greatly reduced, .in accordance with" this invention, by giving to a the inner windings a greater number of turns than the outer windings,=thusrendering the" 00 predom nantmagnetizing force and diverting thefgreaterpart of the stray field to the inner winding, which isnearer the core, the

core. The distribution of: lines is indicated in Fig. 4. It has been found in certain coils that the magnetic fields, due to. opposing currents in the windings, are reduced substantially to a minimum in the space external to the coil when the inner winding has 10% more turns than the outer winding. The percentage, however, will vary according to the design of the loading coil to which the invention is applied, to the class of service for which the coil is designed, and to the conformation of the inclosing case. The proper ratio in each type of coil can be determined by varying the turns of" the inner or the outer winding until the external magnetic forces are substantially reduced to a minimum.

What is claimed is:

1. A loading coil for phantom telephone line systems having an annular core and line windings on a plurality of sections thereof, each line conductor through the coil including windings of opposite core sections, the number of turns in each line conductor being unequally distributed between said opposite core sections.

2. A- loading coil for phantom telephone line systems having an annular core and innerand outer windings on a plurality of sections thereof, each line conductor through the coil 'includingthe inner and the outer windings respectively of opposite core sections, the number of turns in each conductor being unequally distributed between said opposite core sections, whereby the magnetic forces due to opposing currents in said windings are substantially a minimum in the space external to the coil.

3.' A loading coil for phantom telephone line systems having an annular core and inner and outer windings on a plurality of sections thereof, each line conductor through the coil including the inner and the outer windings respectively of opposite core sections, and the number of turns of an inner winding being greater than the number of the outer winding on the same section, whereby the magnetic forces due to opposing currents in said windings are substantially a minimum in the space external to the coil.

4. A loading coil for phantom telephone 1 line systems having an annular core and a plurality ofwindings in layers on each of a plurality of sectionsthereof, each line conductor through the coil including windings of opposite core sections located at different distances from the core, thenumber of turns 7 in each line conductor being unequally, distributed between said opposite core sections,

whereby the 'magnetic forces due to opposing" currents in said windings are sub- 'stantially' aminimuin in the space external to thecoil.

A loading coil"for phantom and tele- J phone line systems having an annular core and inner and outerjwrndmgs on eadi of four quadrants thereof each line conductor I quadrants,

throughthe coil including the inner and the outer windings respectively of opposite core the number of turns in each line conductor. tween. said opposite core quadrants, Whereby the magnetic forces due to opposing currents in said windings are substantially a minimum in-the' space external to the coil.

beingunequally distributed be- In witness whereof, I hereunto subscribe my name this 8th. day of September, A. D. 10 1'914 c WILLIAM MERZ, Witnesses:

JOHNRYAN, v CHAS. RADINI.

Copies of this patent may be obtained for in cents each, by addressing the Commissioner 01' Patents.

' Washington, D. 0." 

